Liquid crystal display device with particular electrodes

ABSTRACT

A display device includes an insulated substrate, a thin film transistor formed over the insulated substrate, and first and second electrodes formed over the insulated substrate. A first insulating layer is formed over the insulated substrate, the first electrode, and the second electrode, and third and fourth electrodes are formed over the first insulating layer. A second insulating layer is formed over the first insulating layer, the third electrode, and the fourth electrode, and a fifth electrode formed over the second insulating layer, and a contact hole is formed in the first insulating layer and the second insulating layer. The fifth electrode is connected to the second electrode via the fourth electrode in the contact hole.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. application Ser. No. 10/926,183, filed Aug.26, 2004, now U.S. Pat. No. 7,084,948, which is a division of U.S.application Ser. No. 10/328,027, filed Dec. 26, 2002, now U.S. Pat. No.6,784,964, the subject matter of which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a so-called in-plane electric field type of liquidcrystal display (LCD) device or a so-called in plane switching (IPS)type of liquid crystal display device.

2. Description of the Related Art

A so-called in-plane electric field type of liquid crystal displaydevice is constituted such that pixel electrodes and counter electrodeswhich generate an electric field therebetween are formed on pixelregions at a liquid-crystal-side surface of one of the respectivesubstrates which are arranged to face each other by way of a liquidcrystal and the liquid crystal is responsive to components of theelectric field substantially parallel to the substrates.

In an active matrix type of liquid crystal display device adopting sucha constitution, first of all, on the liquid-crystal-side surface of theabove-mentioned one substrate, respective regions which are surroundedby a plurality of gate signal lines which are arranged in parallel and aplurality of drain signal lines which cross these respective gate signallines and are arranged in parallel are formed as pixel regions.

Here, each pixel region is provided with a thin film transistor which isoperated in response to a scanning signal from the gate signal line, thepixel electrode to which a video signal is supplied from the drainsignal line through the thin film transistor, and the counter electrodeto which a signal which becomes the reference with respect to the videosignal is supplied.

Here, the pixel electrodes and the counter electrodes are respectivelyformed in a strip-shaped pattern which extend in one direction and theserespective electrodes are formed of two pieces or more in number and areusually arranged alternately.

Further, with respect to such a constitution, there has been also knowna constitution in which the counter electrodes are formed on uppersurfaces of insulation films which are formed so as to cover the drainsignal lines, and the drain signal lines and the center axes of theinsulation films are substantially aligned, and the insulation filmshave a width larger than a width of the drain signal lines, and theinsulation films are formed along the drain signal lines.

Such a constitution is provided for facilitating an electric line offorce from the drain signal lines to terminate at the counter electrodesarranged above the drain signal lines and for preventing the electricline of force from terminating at the pixel electrodes. When theelectric line of force terminates at the pixel electrodes, this givesrise to noises.

On the other hand, the liquid crystal display device having such aconstitution requires counter voltage signal lines for supplying asignal to the counter electrodes and the counter voltage signal linesare arranged to run within the pixel regions so that there has been adrawback that the counter voltage signal lines impede the enhancement ofa so-called numerical aperture of the pixel region.

Further, the counter electrodes and the counter voltage signal lines arearranged by way of an insulation layer in many cases and the electricalconnection between the counter electrodes and the counter voltage signallines is established via small through holes formed in the insulationlayer and hence, the further enhancement of the reliability ofconnection has been requested. This coincides with the demand for highdefinition in recent years.

SUMMARY OF INVENTION

The present invention has been made in view of such circumstances and itis an object of the present invention to provide a liquid crystaldisplay device which can enhance the numerical aperture of pixelregions.

Further, it is another object of the present invention to provide aliquid crystal display device which can ensure the reliable connectionbetween counter electrodes and counter voltage signal lines.

According to a first embodiment of a liquid crystal display device ofthe present invention, there is provided for example, on aliquid-crystal-side surface of one substrate out of respectivesubstrates which are arranged to face each other in an opposed manner byway of liquid crystal, regions which are surrounded by a plurality ofgate signal lines which are arranged in parallel and a plurality ofdrain signal lines which cross the gate signal lines and are arranged inparallel are defined as pixel regions. A switching element is providedwhich is operated in response to a scanning signal from the gate signalline, a pixel electrode to which a video signal is supplied from thedrain signal line through the switching element, and a counter electrodeto which a signal which constitutes the reference with respect to thevideo signal is supplied through a counter signal voltage signal lineare formed on each pixel region. The counter electrodes are formed aslayers below a laminated body consisting of a plurality of insulationlayers, and the counter voltage signal lines are formed of anon-light-transmitting (opaque) conductor, are formed as layers over thelaminated body consisting of the plurality of insulation layers, andform a lattice-like pattern such that the counter voltage signal linescover the gate signal lines and the drain signal lines, and haveportions thereof electrically connected to the counter electrodes viathrough holes formed in the laminated body consisting of the pluralityof insulation layers.

According to a modification of the first embodiment of the liquidcrystal display device of the present invention, for example, theelectric connection between the counter voltage signal line and thecounter electrode is established through another conductive layer whichis formed simultaneously with a conductive layer which constitutes thepixel electrode formed between the plurality of insulation layers.

According to another modification of the first embodiment of the liquidcrystal display device of the present invention, for example, theelectric connection between the counter voltage signal line and thecounter electrode is established through another conductive layer whichis formed simultaneously with a conductive layer which constitutes thedrain signal line formed between the plurality of insulation layers.

According to a further modification of the first embodiment of theliquid crystal display device of the present invention, for example,which may include any of the aforementioned modifications, the electricconnection between the counter voltage signal line and the counterelectrode is established at two or more positions.

According to a second embodiment of the liquid crystal display device ofthe present invention, there is provided on a liquid-crystal-sidesurface of one substrate out of respective substrates which are arrangedto face each other in an opposed manner by way of liquid crystal,regions which are surrounded by a plurality of gate signal lines whichare arranged in parallel and a plurality of drain signal lines whichcross the gate signal lines and are arranged in parallel are defined aspixel regions. A switching element which is operated in response to ascanning signal from the gate signal line, a pixel electrode to which avideo signal is supplied from the drain signal line through theswitching element, and a counter electrode to which a signal whichconstitutes the reference with respect to the video signal is suppliedthrough a counter voltage signal line are formed on each pixel region.The counter electrodes are formed as layers below a laminated bodyconsisting of a plurality of insulation layers, and the pixel electrodesare constituted of a plurality of groups of electrodes which are formedbetween two insulation layers out of the plurality of insulation layersof the laminated body and extend along the extending direction of thedrain signal lines and are arranged in parallel in the direction whichcrosses the extending direction. The counter voltage signal lines areformed of a non-light-transmitting (opaque) conductor, are formed aslayers over the laminated body consisting of the plurality of insulationlayers, and form a lattice-like pattern such that the counter voltagesignal lines cover the gate signal lines and the drain signal lines, andhave portions thereof electrically connected to the counter electrodesvia through holes formed in the laminated body consisting of theplurality of insulation layers.

According to a modification of the second embodiment of the liquidcrystal display device of the present invention, for example, when thepixel region is viewed in plan view, a distance between the countervoltage signal which is formed such that the counter voltage signalcovers the drain signal line and the pixel electrode which is arrangedadjacent to the counter voltage signal line is set larger than adistance between the pixel electrodes which are arranged adjacent toeach other.

According to another modification of the second embodiment of the liquidcrystal display device of the present invention, for example, which mayinclude the aforementioned modifications, when the pixel region isviewed in plan view, a distance between the counter voltage signal linewhich is formed such that the counter voltage signal line covers thedrain signal line and the pixel electrode which is arranged adjacent tothe counter voltage signal line is set larger than a distance betweenthe counter voltage signal and the counter electrode which is arrangedadjacent to the counter voltage signal line.

According to a third embodiment of the liquid crystal display device ofthe present invention, on a liquid-crystal-side surface of one substrateout of respective substrates which are arranged to face each other in anopposed manner by way of liquid crystal, regions which are surrounded bya plurality of gate signal lines which are arranged in parallel and aplurality of drain signal lines which cross the gate signal lines andare arranged in parallel are defined as pixel regions. A switchingelement which is operated in response to a scanning signal from the gatesignal line, a pixel electrode to which a video signal is supplied fromthe drain signal line through the switching element, and a counterelectrode to which a signal which constitutes the reference with respectto the video signal is supplied through a counter voltage signal lineare formed on each pixel region. The counter voltage signal lines aremade of Al or an Al alloy which has a surface thereof anodized and eachcounter voltage signal line is formed as a layer below a laminated bodyconsisting of a plurality of insulation layers. The counter electrodesare formed of a light-transmitting conductor, are formed as layers overthe laminated body consisting of the plurality of insulation layers, andform a lattice-like pattern such that the counter electrodes cover thegate signal lines and the drain signal lines, and have portions thereofelectrically subjected to a capacitive coupling with the counter voltagesignal lines via through holes formed in the laminated body consistingof the plurality of insulation layers.

According to a fourth embodiment of the liquid crystal display device ofthe present invention, on a liquid-crystal-side surface of one substrateout of respective substrates which are arranged to face each other in anopposed manner by way of liquid crystal, regions which are surrounded bya plurality of gate signal lines which are arranged in parallel and aplurality of drain signal lines which cross the gate signal lines andare arranged in parallel are defined as pixel regions,

a switching element which is operated in response to a scanning signalfrom the gate signal line, a pixel electrode to which a video signal issupplied from the drain signal line through the switching element, and acounter electrode to which a signal which constitutes the reference withrespect to the video signal is supplied through a counter voltage signalline are formed on each pixel region. The counter voltage signal linesare made of Al or an Al alloy which has a surface thereof anodized andeach counter voltage signal line is formed as a layer below a laminatedbody consisting of a plurality of insulation layers, and each countervoltage signal line includes conductive material layers which areexposed from the counter voltage signal line at lower layers of at leastportions of the counter voltage signal line. The counter electrodes areformed as layers over the laminated body consisting of the plurality ofinsulation layers, and form a lattice-like pattern such that the counterelectrodes cover the gate signal lines and the drain signal lines, andhave portions thereof electrically connected to the conductive materiallayers via through holes formed in the laminated body consisting of theplurality of insulation layers.

According to a modification of the fourth embodiment of the liquidcrystal display device of the present invention, for example, thecounter electrodes are formed of a light-transmitting conductive layer.

According to another modification of the fourth embodiment of the liquidcrystal display device of the present invention, for example, which mayinclude the aforementioned modifications thereof, the drain signal linesare formed between two insulation layers of the laminated body formed ofthe plurality of insulation layers, and material layers which are madeof the same material as the drain signal lines are interposed betweenthe counter electrodes and the conductive material layers.

Here, the present invention is not limited to the above-mentionedconstitutions and various modifications can be made without departingfrom the technical concept of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view of a liquid crystal display device according tothe present invention and

FIGS. 1B, 1C and 1D are sectional views of FIG. 1A taken along lines 1b, 1 c and 1 d, separately.

FIG. 2A is a view of the liquid crystal display device according to thepresent invention, and

FIG. 2B is an enlarged view of a portion of 2 b.

FIG. 3 is a cross-sectional view of the pixel of the liquid crystaldisplay device according to the present invention.

FIG. 4 is a cross-sectional view of the pixel of another liquid crystaldisplay device according to the present invention.

FIG. 5 is a cross-sectional view of the pixel of another liquid crystaldisplay device according to the present invention.

FIG. 6 is a plan view of the pixel of another liquid crystal displaydevice according to the present invention.

FIG. 7A is a plan view of the pixel of another liquid crystal displaydevice according to the present invention and

FIG. 7B is a sectional view taken along line 7 b.

FIG. 8 is a cross-sectional view of the pixel of another liquid crystaldisplay device according to the present invention.

FIG. 9A is a plan view of the pixel of another liquid crystal displaydevice according to the present invention and

FIG. 9B is a sectional view taken along line 9 b.

FIG. 10 is a cross-sectional view of the pixel of another liquid crystaldisplay device according to the present invention.

FIG. 11A is a plan view of the pixel of another liquid crystal displaydevice according to the present invention and

FIG. 11B is a sectional view taken along line 11 b.

FIG. 12 is a cross-sectional view of the pixel of another liquid crystaldisplay device according to the present invention.

FIG. 13A is a plan view of the pixel of another liquid crystal displaydevice according to the present invention and

FIG. 13B is a sectional view taken along line 13 b.

FIG. 14 is a cross-sectional view of the pixel of another liquid crystaldisplay device according to the present invention.

FIGS. 15A-15C are explanatory views showing different arrangements ofcontact holes of the pixel of the liquid crystal display deviceaccording to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a liquid crystal display device according tothe present invention are explained hereinafter in conjunction withattached drawings.

Embodiment 1

<<Overall Constitution>>

FIG. 2A is a view showing one embodiment of a liquid crystal displaydevice according to the present invention. Although the drawing is anequivalent circuit diagram, the drawing is depicted in accordance withan actual geometrical arrangement.

In the drawing, there are provided a pair of transparent substratesSUB1, SUB2 which are arranged to face each other by way of liquidcrystal and the liquid crystal is sealed by a sealing member SL which isalso served for fixing the other transparent substrate SUB2 to onetransparent substrate SUB1.

On a liquid-crystal-side surface of the above-mentioned one transparentsubstrate SUB1 which is surrounded by the sealing member SL, gate signallines GL which extend in the x direction and are arranged in parallel inthe y direction and drain signal lines DL which extend in the ydirection and are arranged in parallel in the x direction are formed.

Regions which are surrounded by respective gate signal lines GL andrespective drain signal lines DL constitute pixel regions and a mass ofthese respective pixel regions in a matrix array constitutes a liquidcrystal display part AR.

Further, in respective pixel regions which are arranged in parallel inthe x direction, a common counter voltage signal line CL which runswithin respective pixel regions is formed. This counter voltage signalline CL is served as a signal line for supplying a voltage whichconstitutes the reference with respect to a video signal to counterelectrodes CT of respective pixel regions which will be described later.

On each pixel region, a thin film transistor TFT which is operated inresponse to a scanning signal supplied from one-side gate signal line GLand a pixel electrode PX to which the video signal is supplied fromone-side drain signal line DL by way of the thin film transistor TFT areformed as shown in enlarged view of FIG. 2B.

This pixel electrode PX generates an electric field between the pixelelectrode PX and the counter electrode CT which is connected to thecounter voltage signal line CL and the light transmittivity of theliquid crystal is controlled in response to this electric field.

Respective one ends of the above-mentioned gate signal lines GL extendover the sealing member SL and extending ends thereof constituteterminals to which output terminals of a vertical scanning drivingcircuit V are connected. Further, input terminals of the verticalscanning driving circuit V are configured to receive input of signalsfrom a printed circuit board arranged outside the liquid crystal displaypanel.

The vertical scanning driving circuit V is constituted of a plurality ofsemiconductor devices, wherein a plurality of gate signal lines GL whichare arranged close to each other are formed into a groups and onesemiconductor device is allocated to each group.

In the same manner, respective one ends of the drain signal lines DLextend over the sealing member SL and extending ends constituteterminals to which output terminals of the video signal driving circuitHe are connected. Further, input terminals of the video signal drivingcircuit He receive input of signals from a printed circuit board whichare arranged outside the liquid crystal display panel.

The video signal driving circuit He is also constituted of a pluralityof semiconductor devices, wherein a plurality of drain signal lines DLwhich are arranged close to each other are formed into a groups and onesemiconductor device is allocated to each group.

Further, respective counter voltage signal lines CL have end portionsthereof arranged at the right side in the drawing connected in common,and the connection line extends over the sealing member SL and theextending ends constitutes a terminal CLT. A voltage which becomes thereference with respect to the video signal is supplied from thisterminal CLT.

With respect to respective gate signal lines GL, in response to thescanning signal from the vertical scanning circuit V, one of the gatesignal lines GL is sequentially selected.

Further, to respective drain signal lines DL, using the video signaldriving circuit He, the video signals are supplied in accordance withthe timing of selecting the gate signal line GL.

Here, in the above-mentioned embodiment, although the vertical scanningdriving circuit V and the video signal driving circuit He areconstituted of the semiconductor devices mounted on the transparentsubstrate SUB1, these circuits may be constituted of so-called tapecarrier type semiconductor devices which establish connections whilestriding over a span between the transparent substrate SUB1 and theprinted circuit board, for example. Further, when a semiconductor layerof the thin film transistor TFT is constituted of polycrystallinesilicon (p-Si), these circuits may be constituted such that thesemiconductor dies which are formed of the polycrystalline silicon areformed on a transparent substrate SUB1 surface along with wiring layers.

<<Constitution of Pixels>>

FIG. 1A is a plan view showing the constitution of one embodiment of thepixel regions. Further, FIG. 1B is a cross-sectional view taken along aline 1 b-1 b in FIG. 1A, FIG. 1C is a cross-sectional view taken along aline 1 c-1 c in FIG. 1A, and FIG. 1D is a cross-sectional view takenalong a line 1 d-1 d of FIG. 1A.

In respective drawings, on the liquid-crystal-side surface of thetransparent substrate SUB1, first of all, a pair of gate signal lines GLwhich extend in the x direction and are arranged in parallel in the ydirection are formed.

These gate signal lines GL surround a rectangular region along with apair of drain signal lines DL which will be described later and theregion is constituted as the pixel region.

Then, on the surface of the transparent substrate SUB1 within the pixelregion, the counter electrode CT which is formed of a light-transmittingconductive material is formed on a center portion excluding a smallregion defined in the periphery of the pixel region. As thelight-transmitting conductor, for example, ITO (Indium Tin Oxide), ITZO(Indium Tin Zinc Oxide), IZO (Indium Zinc Oxide), SNO₂, IN₂O₃ or thelike is used.

On the surface of the transparent substrate SUB1 on which the gatesignal lines GL and the counter electrodes CT are formed, an insulationfilm GI made of SiN, for example, is formed such that the insulationfilm GI covers the gate signal line GL and the like.

The insulation film GI performs a function of an interlayer insulationfilm with respect to the gate signal lines GL in regions where the drainsignal lines DL which will be described later are formed and performs afunction of a gate insulation film in regions where the thin filmtransistors TFT which will be described later are formed.

Here, on a surface of the insulation film GI, semiconductor layers ASmade of amorphous Si, for example, are formed such that thesemiconductor layers AS are overlapped to portions of the gate signallines DL.

The semiconductor layer AS forms a portion of the thin film transistorTFT and it is possible to constitute an MIS type of transistor having aninverse staggering structure which uses a portion of the gate signalline as a gate electrode by forming a drain electrode SD1 and a sourceelectrode SD2 on an upper surface thereof.

Here, the drain electrodes SD1 and the source electrodes SD2 aresimultaneously formed along with the formation of the drain signal linesDL.

That is, the drain signal lines DL which extend in the y direction andare arranged in parallel in the x direction are formed, portions of thedrain signal lines DL are extended onto the upper surfaces of thesemiconductor layers AS so as to form the drain electrodes SD1, and thesource electrodes SD2 are formed in such a manner that they are spacedapart from the drain electrodes SD1 by a length of a channel of the thinfilm transistor TFT.

Further, the source electrode SD2 is slightly extended toward the pixelregion side so as to form a contact portion COT for establishing theelectrical connection with the pixel electrodes PX which will bedescribed later.

Then, on the surface of the transparent substrate SUB1, a protectivefilm PSV1 is formed such that the protective film PSV1 covers the drainsignal lines DL, the drain electrodes SD1 and the source electrodes SD2.The protective film PSV1 is made of an inorganic material layer such asan SiN film or the like, for example, and is provided for obviating thedirect contact of the thin film transistors TFT with the liquid crystalalong with a protective film PSV2 described later. That is, theprotective film PSV1 is provided for preventing the characteristics ofthe thin film transistors TFT from being changed due to the directcontact with the liquid crystal.

On a surface of the protective film PSV1, the pixel electrodes PX whichare made of a light-transmitting conductor, for example, are formed. Asthe light-transmitting conductor, ITO (Indium Tin Oxide), ITZO (IndiumTin Zinc Oxide), IZO (Indium Zinc Oxide), SnO2, In2O3 and the like areused.

Here, although the pixel electrode PX is formed of a large number ofstrip-like electrodes which substantially extend in the x direction andare arranged in the y direction, each electrode is formed in amountain-shaped pattern having a bent portion substantially at a centerportion of the extending direction of the electrode.

Although these pixel electrodes PX are configured to generate anelectric field between peripheral end portions (edges) thereof and thecounter electrodes CT, with the use of the above-mentioned pattern, theliquid crystal display device adopts a so-called multi-domain method.

That is, even when the molecular arrangement of the liquid crystal is inthe same state, the polarization state of the transmitting light ischanged depending on the incident direction of the light incident on theliquid crystal display panel and hence, the light transmissivity ischanged in response to the incident direction.

Such viewing angle dependency of the liquid crystal display panel hasthe display characteristics that when a viewing point is slantedobliquely with respect to the viewing angle direction, an invertingphenomenon of luminance is induced so that images are stained in colordisplay.

Accordingly, the pixel electrodes PX are patterned such that each pixelelectrode PX has at least one bent portion in the extension directionthereof and the counter electrodes CT are formed in a shape which shiftssuch a pattern in parallel, and using an imaginary line which is formedby binding the bent points of respective electrodes as a boundary, thedirections of the electric fields acting between the pixel electrodes PXand the counter electrodes CT are made different from each other betweenone region and the other region, whereby the stain of images generateddepending on the viewing angle is compensated.

Although the counter electrode CT is formed on the substantially wholearea of the pixel region in this embodiment, a portion which actuallyperforms the function of the counter electrode CT is a portion where thepixel electrode PX is shifted in parallel as described above. It ispossible to connect the counter electrode of one pixel region to acounter electrode of the next pixel region.

Then, since a group of electrodes which constitute the pixel electrodePX are electrically connected to each other, they are integrally formedin a periphery thereof using the same material. Accordingly, the pixelelectrode PX is, as a whole, configured as a pattern in which a largenumber of slits (mountain-like slits) which extend in the x directionand are arranged in parallel in the y direction are formed in theconductive layer at the center portion of the pixel region except for aminute region in the periphery of the pixel region.

A portion of the pixel electrode PX having such a pattern iselectrically connected to the contact portion COT of the sourceelectrode SD2 of the thin film transistor TFT via a through hole whichis preliminarily formed in the protective film PSV1.

Further, on the surface of the transparent substrate SUB1, theprotective film PSV2 is formed such that the protective film PSV2 coversthe pixel electrodes PX. The protective film PSV2 is made of organicmaterial such as resin, for example.

As has been described above, the protective film PSV2 has a function ofa protective film PSV for obviating the direct contact of the thin filmtransistors TFT with the liquid crystal along with the protective filmPSV1. Here, by using organic material as a material of the protectivefilm PSV2, the surface of the protective film PSV2 can be leveled sothat the rubbing characteristics of an orientation film formed over anupper surface of the protective film PSV2 can be enhanced.

Further, on the surface of the protective film PSV2, the counter voltagesignal lines CL served for supplying signals to the counter electrodesCT are formed.

As a material of the counter voltage signal lines CL, a material havingsmall electric resistance is selected. Accordingly, metal or the like ispreferably used.

Further, the counter voltage signal lines CL define a lattice-like(matrix) pattern which covers the drain signal lines DL and the gatesignal lines GL, wherein opening portions are formed in the centerportion of the pixel regions excluding the minute portions around thepixel regions. That is, the counter voltage signal lines CL are formedsuch that the pixel regions are substantially exposed. The matrixpattern of the counter voltage signal lines reduces the resistance ofthe counter voltage signal lines and shields the electric field of gatesignal lines and drain signal lines. The counter voltage signal linescover all of the drain signal lines and a part of gate signal line.

The counter voltage signal lines CL which are formed in such a patterncan supply the counter voltage signals from any portion or from aplurality of portions in the periphery of each liquid crystal displaypart AR. Accordingly, it is possible to eliminate the waveformdistortion of the counter voltage signals in the counter voltage signallines CL whereby the occurrence of smear and luminance inclination canbe reduced.

Further, since the electric resistance and the feeding resistance of thecounter voltage signal lines CL can be reduced as a whole, it ispossible to reduce the transverse smear to equal to or less than ⅓ in aso-called common inverting driving.

Further, the counter voltage signal lines CL which cover the drainsignal lines DL along the longitudinal direction of the drain signallines DL have center axes thereof substantially aligned with the centeraxes of the drain signal lines DL and have a width larger than that ofthe drain signal lines DL. Due to such a constitution, an electric fieldwhich becomes a cause of noises from the drain signal lines DL can beterminated at the counter voltage signal line CL side, while thetermination of the electric field at the pixel electrodes PX is madedifficult.

In this case, the parasitic capacitance between the drain signal linesDL and the counter voltage signal lines CL can be largely reduced due tothe protective film PSV2 made of organic material which is interposedbetween the drain signal lines DL and the counter voltage signal linesCL. This is because that the protective film PSV2 exhibits the smalldielectric constant.

In the same manner, the counter voltage signal lines CL which cover thedrain signal lines DL along the longitudinal direction of the drainsignal lines DL have center axes thereof substantially aligned with thecenter axes of the drain signal lines DL and have a width larger thanthat of the drain signal lines DL.

In this case, the counter voltage signal lines CL are formed such thatthe counter voltage signal lines CL also cover the thin film transistorsTFT. The counter voltage signal lines CL are made ofnon-light-transmitting metal. This is because that the counter voltagesignal lines CL can shield an external light irradiated to the thin filmtransistors TFT so as to prevent the degradation of the characteristicsof the thin film transistor TFT.

Here, the counter voltage signal line CL is configured to have a regionwhich is overlapped to a portion of the pixel electrode PX within thepixel region. On this overlapped region, a capacitive element Cstg whichuses the protective film PSV2 as a dielectric film is formed.

The capacitive element Cstg is configured to have a function of storingthe video signals supplied to the pixel electrode PX, for example, for arelatively long period.

Then, on the upper surface of the transparent substrate SUB1 on whichthe counter electrodes CT are formed in this manner, an orientation film(not shown) is formed such that the orientation film covers the counterelectrodes CT. The orientation film is a film which is brought intodirect contact with the liquid crystal and determines the initialorientation direction of the liquid crystal molecules by rubbing formedon the surface thereof.

Here, on a liquid-crystal-side surface of the transparent substrate SUB2which is arranged to face the transparent substrate SUB1 by way of theliquid crystal, color filters are formed. The color filters are, forexample, constituted of filters of respective colors such as red (R),green (G), blue (B) and formed in an arrangement where, for example, thered color filters are commonly formed in a group of respective pixelregions which are arranged in parallel in the y direction, and inrespective neighboring groups of pixel regions which are arranged in thex direction adjacent to the previous group of pixel regions, the groupsof pixel regions are arranged in the order of the group of red (R), thegroup of green (G), the group of blue (B), the group of red (R), . . .

A leveling film is formed on the surface of the transparent substrate onwhich the color filters are formed such that the leveling film coversthe color filters. The leveling film is constituted of a resin filmformed by coating and is provided for eliminating stepped portions whichbecome apparent in the course of the formation of the color filters.

An orientation film is formed on a surface of the leveling film. Theorientation film is a film which is brought into direct contact with theliquid crystal and determines the initial orientation direction of theliquid crystal molecules by rubbing formed on a surface thereof.

In this embodiment, a black matrix is not formed on theliquid-crystal-side surface of the transparent substrate SUB2. This isbecause that the counter voltage signal lines CL which are formed on theliquid-crystal-side surface of the transparent substrate SUB1 perform afunction similar to a function of the black matrix. Accordingly, it ispossible to enhance the accuracy of the alignment of the transparentsubstrate SUB2 with respect to the transparent substrate SUB1.

Embodiment 2

FIG. 3 is a cross-sectional view of the pixel of another liquid crystaldisplay device of the present invention and is a view corresponding toFIG. 1B.

The difference of FIG. 3 from that shown in FIG. 1B lies in that in theconnection between the counter electrode CT and the counter voltagesignal line CL via a through hole TH, a conductive layer CNL which ismade of the same material as a material layer which constitutes a pixelelectrode PX is interposed between the counter electrode CT and thecounter voltage signal line CL. The material comprises a portion whichis same level of the pixel electrode. The level means a distance fromthe substrate.

That is, at the time of forming the pixel electrodes PX on the uppersurface of the protective film PSV1, the conductive layer CNL which isconnected to the counter electrode CT via the through hole TH1 formed inthe protective film PSV1 is simultaneously formed and, thereafter, thecounter voltage signal lines CL which are formed on the upper surface ofthe protective film PSV2 are connected to the conductive layer CNL viathe through hole TH2 formed in the protective film PSV2.

Due to such a constitution, it is possible to increase the contact areaof the connecting portion between the counter electrode CT and thecounter voltage signal line CL so that the reliable connection can beachieved.

Embodiment 3

FIG. 4 is a cross-sectional view of the pixel of another liquid crystaldisplay device of the present invention and is a view corresponding toFIG. 3.

The difference of FIG. 4 from that of FIG. 3 lies in that in theconnection between the counter electrode CT and the counter voltagesignal line CL via a through hole TH, a conductive layer CNL which ismade of the same material as a material layer of the drain signal lineDL is interposed between the counter electrode CT and the countervoltage signal line CL.

When a conductor having a light transmissivity is used as the materialof the counter electrode CT and, for example, Al or an Al alloy is usedas the material of the counter voltage signal line CL, there is apossibility that the connection resistance assumes a large value.Accordingly, in this embodiment, for example, Cr, Mo, W or other highmelting point metal or an alloy containing them are used as the materialof the drain signal line DL. Due to such a constitution, it is possibleto reduce the connection resistance between the counter electrode CT andthe counter voltage signal line CL.

Embodiment 4

FIG. 5 is a cross-sectional view of the pixel of another liquid crystaldisplay device of the present invention and is a view corresponding toFIG. 3.

The difference of FIG. 5 from FIG. 3 lies in that the center axis of thethrough hole TH1 which is formed in the protective film PSV1 and theinsulation film GI and the center axis of the through hole TH2 which isformed in the insulation film PSV2 are not aligned and these holes TH1,TH2 are formed at positions separate from each other.

Due to such a constitution, it is possible to level the surface of theprotective film PSV2 made of organic material even at positions wherethe protective film PSV1 and the through hole TH1 of the insulation filmGI are formed.

This implies that the recessed portion formed in the protective filmPVS2 is formed of only the through hole TH2. Since a depth of thethrough hole TH2 is relatively small, it is possible to enhance therubbing characteristics of the orientation film formed on the surface ofthe protective film PSV2.

Embodiment 5

FIG. 6 is a plan view of the pixel of another liquid crystal displaydevice of the present invention and is a view corresponding to FIG. 1A.

The difference of FIG. 6 from FIG. 1A lies in that portions where theconnection between the counter electrode CT and the counter voltagesignal line CL is established are provided at two positions instead ofone position.

As can be clearly understood from the above-mentioned constitutions, theconnection between the counter electrode CT and the counter voltagesignal line CL must be established via the through holes TH formed in arelatively multi-layered body consisting of the protective films PSV2,PSV1 and the insulation film GI and hence, the redundancy constitutionwhich can obviate the occurrence of connection failure is established.

Further, in this embodiment, one through hole TH is formed in thevicinity of one gate signal line GL which surrounds the pixel region andthe other through hole TH is formed in the vicinity of the other gatesignal line GL which surrounds the pixel region.

Embodiment 6

FIG. 7A is a plan view showing the pixel of another liquid crystaldisplay device of the present invention and is a view corresponding toFIG. 1A. On the other hand, FIG. 7B is a cross-sectional view takenalong a line 7 b-7 b in FIG. 7A.

The difference FIG. 7A from FIG. 1A lies in the constitution of thepixel electrodes PX. That is, in this embodiment, the pixel electrodesPX is constituted of a group of electrodes which extend in the ydirection substantially linearly and are arranged in the x direction inparallel.

Also in this embodiment, each pixel electrode PX formed of a group ofelectrodes has upper and lower ends of the electrodes connected to eachother.

Further, the protective film PSV2 is formed such that protective filmPSV2 covers these pixel electrodes PX, while the counter voltage signallines CL are formed over the upper surface of the protective film PSV2such that the counter voltage signal lines CL cover the drain signallines DL and the gate signal lines GL.

Due to such a constitution, among the respective electrodes of pixelelectrode PX which are formed in the inside of the region of the openingportion of the counter voltage signal line CL, the electrode of thepixel electrode PX which is arranged adjacent to the drain signal lineDL can be arranged closer to the counter voltage signal line CL.Accordingly, it is possible to give the function of the counterelectrode CT to the counter voltage signal line CL such that an electricfield is generated between the drain signal line DL and the countervoltage signal line CL.

with such constitution, it is possible to form the pixel region withoutforming an unnecessary region in the region of the opening portion ofthe counter voltage signal line CL whereby the numerical aperture can beenhanced.

That is, the electric field from the drain signal line DL is terminatedat the counter voltage signal line CL side which is formed over thedrain signal line DL in a substantially concentrated manner and hence,an amount of the electric field which spreads radially at both sides ofthe counter voltage signal line CL is reduced. Accordingly, it ispossible to constitute the pixel region which can contribute to thedisplay even in the vicinity of the counter voltage signal line CL.

Further, by adopting the above-mentioned constitution, as shown in FIG.8 which corresponds to FIG. 7B, it is possible to set a distance W1between the counter voltage signal line CL and the pixel electrode PXwhich is arranged close to the counter voltage signal line CL to a valuedifferent from a distance W2 between respective pixel electrodes PX.This implies that when the number of the pixel electrodes PX is alreadyfixed and the distance between the pixel region can be variably set, theoptimum pixel constitution can be easily realized by adjusting thedistance W1 between the counter voltage signal line CL and the pixelelectrode PX which is arranged close to the counter voltage signal lineCL.

Further, since the counter voltage signal lines CL are formed over theupper surface of the protective film PSV2 having a small dielectricconstant, the field strength between the counter voltage signal line CLand the pixel electrode PX which is arranged close to the countervoltage signal line CL can be made larger than the field strengthbetween the counter electrode CT and the pixel electrode PX.Accordingly, to make the luminance in the inside of the pixel uniform,it is preferable to set the relationship between distances W1 and W2 toW1>W2. Further, assuming a film thickness of the protective film PSV2 asd, it is preferable to set the relationship between distances W1 and W2to W1>W2+d.

Further, to reduce noises from the drain signal line DL, it ispreferable to set the relationship between distances W1 and W3 to W1>W3as shown in FIG. 8. Here, W3 is a space-apart distance between thecounter voltage signal line CL and the counter electrode CT arrangedclose to the counter voltage signal line CL. Due to such a constitution,the noise electric field from the drain signal line DL is confined to anequi-potential surface of the counter voltage signal line CL and thecounter electrode CT having the equal potential so that leaking of noiseelectric field to the outside can be suppressed.

Here, it is preferable to form the counter voltage signal line CL suchthat the counter voltage signal line CL has sides thereof arrangedparallel to the running direction of the drain signal line DL projectedfrom the drain signal line DL by an amount equal to or more than ⅓×W1.

The above-mentioned embodiment can adopt a multi-domain method byproviding one or a plurality of bent portions to respective pixelelectrodes PX in the longitudinal direction. In this case, along withthe adoption of the multi-domain method, by adopting a pattern in whichthe drain signal line DL and the counter voltage signal line CL havebent portions in the same manner as the pixel electrodes PX which areshifted in the x direction, it is possible to obtain the above-mentionedadvantageous effects.

Embodiment 7

FIG. 9A is a plan view showing the pixel of another liquid crystaldisplay device of the present invention and is a view corresponding toFIG. 7A. On the other hand, FIG. 9B is a cross-sectional view takenalong a line 9 b-9 b in FIG. 9A.

The difference of FIG. 9A from FIG. 7A is, first of all, that the pixelelectrodes PX are formed on the same layer as the drain signal lines DLover the insulation film GI.

Further, the protective film PSV1 and the protective film PSV2 aresequentially formed on the insulation film GI such that these protectivefilm PSV1, PSV2 also cover the pixel electrodes PX and the drain signallines DL, and the counter electrodes CT having a lattice-like patternare formed on the upper surface of the protective film PSV2 such thatthe counter electrodes CT also covers the drain signal lines DL and thegate signal lines GL.

Further, the counter electrodes CT are electrically connected to thecounter voltage signal lines CL which are formed as a layer below theinsulation film GI via the through holes TH formed in the protectivefilm PSV2, the protective film PSV1 and the insulation film GI in apenetrating manner.

Here adopted is a multi-domain method in which the pixel electrodes PXand the counter electrodes CT (drain signal lines DL) have a pluralityof bent portions along the running direction thereof.

In this case, the counter voltage signal lines CL are simultaneouslyformed at the time of forming the gate signal lines GL. It is preferablethat the counter voltage signal lines CL are made of Al or an AL alloylayer, for example, and an oxide film AO is formed on a surface thereofby anodizing.

In this embodiment, the through holes TH are formed in the protectivefilm PSV2, the protective film PSV1 and the insulation film GI in such amanner that portions of the anodized counter voltage signal lines CL areexposed and the counter electrodes CT are formed such that the counterelectrodes CT cover the through holes TH.

That is, the electric connection between the counter electrodes CT andthe counter voltage signal lines Cl is performed by the capacitivecoupling via the oxide film AO so that it is not specifically necessaryto remove the oxide film AO.

Since the counter electrodes CT adopt a lattice-like pattern, it ispossible to supply electricity from these counter electrodes CT andhence, the counter electrodes CT play a role of stabilizing a so-calledcommon potential even when electricity is not directly supplied to thecounter voltage signal lines CL.

In view of the above, as shown in FIG. 10, it is possible to furtherinsert a conductive layer CNL made of the same material as the drainsignal lines DL between the electrical connecting portions of theanodized counter voltage signal lines CL and the counter electrodes CT.

Further, in forming such a capacitive coupling constitution, the countervoltage signal lines CL and the counter electrodes CT may differ inmaterial from each other. This is because that even when a stress isgenerated between them and a crack occurs at a joint portion, it ispossible to ensure the direct electrical connection.

Embodiment 8

FIG. 11A is a plan view of the pixel of another liquid crystal displaydevice of the present invention and is a view corresponding to FIG. 9A.On the other hand, FIG. 11B is a cross-sectional view taken along a line11 b-11 b in FIG. 11A.

Compared with the embodiment shown in FIG. 9A, the counter voltagesignal lines CL are made of Al (or Mo, Ti, Ta, W, Zr, Si or an alloycontaining one or a plurality of these metals) and the oxide film AO isformed on the counter voltage signal line CL by anodizing in the samemanner. On the other hand, this embodiment differs from the embodimentshown in FIG. 9A in that another conductive layer CNL made of metalother than Al or the Al alloy (for example, Cr, Mo, W, Ti, Zr or alloycontaining one or more of these metals) is formed below a portion of theoxide film AO, and the conductive layer CNL is formed such that theconductive layer CNL extends to a region other than a region where thecounter voltage signal line CL is formed.

The extending portion of the conductive layer CNL is configured tofunction as a contact portion which comes into contact with the counterelectrode CT. Due to such a constitution, even when the counter voltagesignal line CL is anodized, the metal layer is not anodized and hence,it is possible to form a terminal portion which can ensure thesufficient electric connection between the metal layer and the countervoltage signal line CL.

Here, the conductive layer CNL is formed over a whole area of the regionwhere the counter voltage signal line CL is formed at portions exceptfor the extending portions. In other words, the conductive layer CNL maybe formed in the same pattern as the counter voltage signal line CLwhere an extension portion is formed at a portion thereof.

FIG. 12 is a cross-sectional view showing the pixel of another liquidcrystal display device according to the present invention and is a viewwhich corresponds to FIG. 11B.

In this embodiment, the electric connection between the conductive layerCNL and the counter electrode CT is established through a conductivelayer CNL2 made of the same material as the material layer of the drainsignal line DL.

Due to such a constitution, the contact area between the metal layer andthe counter electrode CT can be increased so that the reliability of theconnection can be enhanced.

Embodiment 9

As another embodiment of the constitution described in theabove-mentioned embodiment 8, the metal layer may be replaced with alight-transmitting conductive layer such as ITO, IZO or the like.

In this case, since the counter electrode CT is also made of thelight-transmitting layer, it is possible to have an advantageous effectthat even when the area of the contact portion between them isincreased, the numerical aperture of the pixel region is not reduced.

Embodiment 10

FIG. 13A is a plan view of the pixel of another liquid crystal displaydevice of the present invention and is a view corresponding to FIG. 11A.On the other hand, FIG. 13B is a cross-sectional view taken along a line13 b-13 b in FIG. 13A.

The difference of FIG. 13A from FIG. 11A lies in that at the electricconnecting portion between the counter electrode CT and the countervoltage signal line CL, the oxide film AO which is formed on the surfaceof the counter voltage signal line CL is configured such that the oxidefilm AO is not partially formed at the time of anodizing.

That is, by immersing the whole transparent substrate SUB1 on which thecounter voltage signal lines CL are formed into an electrolytic solutionand by applying a voltage in a state that the counter voltage signalline CL forms one electrode and another separately-prepared electrodeplate immersed in the electrolytic solution forms another electrode(anodizing), the anodic oxide film is formed on the surface of thecounter voltage signal line CL.

In this case, at the connecting portion between the counter voltagesignal line CL and the counter electrode CT, the anodizing is performedin a state that a resist film is selectively formed. By removing theresist film at a stage that the anodizing is completed, it is possibleto obtain the counter voltage signal line CL which exposes the surfacemade of Al or the AL alloy at removed portions thereof.

The resist film is formed by a usual exposure treatment in which a photoresist is formed on the entire surface of the counter voltage signalline CL, then the exposure is performed using a mask exposure, andfinally an unnecessary resist is removed.

In this case, it is preferable that the counter electrode CT is formednot only on the portion of the counter voltage signal line CL where theoxide film AO is removed but also on a region where the oxide film AO isformed.

Otherwise, Al or the Al alloy which is not anodized directly faces theinsulation film GI and hence, there is a possibility that hillockoccurs.

Embodiment 11

FIG. 14 is a cross-sectional view the pixel of another liquid crystaldisplay device according to the present invention and is a view whichcorresponds to FIG. 13B.

The difference of FIG. 14 from that of FIG. 13B lies in that inconnecting the counter electrode CT and the counter voltage signal lineCL, the conductive layer CNL which is made of the same material as thematerial of the drain signal line DL which is formed on the insulationfilm GI is interposed.

Due to such a constitution, the direct connection between Al or an ALalloy of the counter voltage signal line CL and the light-transmittingconductive layer made of ITO or the like can be obviated and hence, theincrease of the connection resistance can be suppressed. This is becausethat the light-transmitting conductive layer is an oxide and hence, whenthe conductive layer is brought into direct contact with Al or the Alalloy, Al or the Al alloy is oxidized and the connection resistance isincreased.

Embodiment 12

FIG. 15A to FIG. 15C are plan views of another liquid crystal displaydevice according to the present invention.

The circle in the drawings show contact holes connecting between thecounter voltage signal line CL and the counter electrode CT and thedotted line outline represents a dot comprised of three pixels (red,green and blue for display). In FIG. 15A, the contact hole connectingbetween the counter voltage signal line CL and the counter electrode CTis made for every pixel of the dot. In FIG. 15B, the connection betweenthe counter voltage signal line CL and the counter electrode CT is madeat alternate pixels of a dot. In FIG. 15C, the contact holes connectingbetween the counter voltage signal line CL and the counter electrode CTis made at one pixel of each dot.

As mentioned above, the counter voltage signal lines CL or the counterelectrodes CT are formed in a lattice-like pattern which definesrespective pixel regions and hence, the connection between the countervoltage signal lines CL and the counter electrodes CT can be setarbitrarily in terms of position as well as number.

However, by positioning the connection between the counter voltagesignal lines CL and the counter electrodes CT within the pixels whichexhibit relatively high luminance, the influence of such connection tothe luminance can be prevented.

Further, when so-called columnar spacers are arranged between thetransparent substrate SUB1 and the transparent substrate SUB2 and areformed on either one of these substrates, the pixel regions where thespacers are formed and the pixel regions where the connection betweenthe counter voltage signal lines CL or the counter electrodes CT isestablished may be separately provided.

Due to such a constitution, it is possible to prevent the stereoscopicstructure of the specific pixel regions from becoming relativelycomplicated compared to the corresponding structure of other pixels andhence, it is possible to obviate in advance the possibility that anunpredicted failure occurs only on the particular pixels due to thedifference in the stereoscopic structure.

As has been described heretofore, according to the liquid crystaldisplay device of the present invention, it is possible to enhance thenumerical aperture of the pixel regions. Further, the reliableconnection between the counter electrode and the counter voltage signalline can be ensured.

1. A display device comprising: an insulated substrate; a thin filmtransistor formed over the insulated substrate; a first electrode formedover the insulated substrate and connected to one terminal of the thinfilm transistor; a second electrode formed over the insulated substrateand formed of a same material as a material of the first electrode; afirst insulating layer formed over the insulated substrate, the firstelectrode, and the second electrode; a third electrode formed over thefirst insulating layer and connected to another terminal of the thinfilm transistor; a fourth electrode formed over the first insulatinglayer, and formed of a same material as a material of the thirdelectrode; a second insulating layer formed over the first insulatinglayer, the third electrode, and the fourth electrode; a fifth electrodeformed over the second insulating layer; and a contact hole formed inthe first insulating layer and the second insulating layer; wherein thefifth electrode is connected to the second electrode via the fourthelectrode in the contact hole.
 2. A display device according to claim 1,wherein when the insulated substrate is viewed in plan view, a portionof the contact hole of the first insulating layer is different from aportion of the contact hole of the second insulating layer.
 3. A displaydevice according to claim 1, wherein the first electrode and the secondelectrode comprise one of an Al layer and an Al alloy layer having ananodized surface, and the fifth electrode and the fourth electrode areconnected by a capacitive coupling with the second electrode in thecontact hole.
 4. A display device according to claim 1, wherein thefirst electrode and the second electrode comprise one of an Al layer andan Al alloy layer having an anodized surface, and the second electrodecomprises a conductive layer formed below the one of the Al layer andthe Al alloy layer and exposed from the one of the Al layer and the Alalloy layer, and the fifth electrode is electrically connected to theconductive layer of the second electrode via the fourth electrode in thecontact hole.